As generally known in the art, display devices are evolving toward better screen quality and a larger screen size in line with the improvement of living standards and the remarkable development of electronic technology. CRTs (cathode ray tubes), also referred to as Braun tubes, have been widely used as typical display devices acting as the final medium of conveying various pieces of information (e.g. TVs, computers), but there are technical limits in various aspects, particularly when it comes to making display devices of forty inches or larger.
That is to say, Braun tubes over forty inches are not only difficult to manufacture, but inevitably have an excessive thickness (and, therefore, overall volume) when made in such a large size. Such excessive size and weight limit the installation space, and make transportation and handling difficult.
Therefore, various types of flat display panels have been developed, which are thin enough to be hung on a wall (i.e. little limitations on the installation space) and which have a screen size of forty inches or larger. Flat display panels are classified into those capable of emitting light on their own, including FED (field emission display) panels, EL (electroluminescence) panels, and PDPs (plasma display panels), and those incapable of emitting light on their own, including LCD (liquid crystal display) panels and ECD (electrochromic display) panels.
Among the above-mentioned flat display panels, PDPs and LCD panels are drawing the most attention recently, and are evolving fast enough to be used for TVs of fifty inches or larger.
Both PDP and LCD panel manufacturers are fiercely competing to dominate the large TV market, and, as a result, the PDP manufacturers have succeeded in reducing power consumption to some extent, and the LCD panel manufacturers in making larger panels. Although LCD panels have the drawback of having residual images burned into the screen when moving images are played, they are superior to PDPs in terms of power consumption and smoothness of images, and are prevailing in the TV market of fifty inches or less.
As LCD panels have become widespread as mentioned above, manufacturers are competing to reduce the manufacturing cost and develop panels that are light and slim enough to be hung on the wall. However, conventional metal reinforcement frames used to reinforce display panels (e.g. LCD panels, PDPs) have the following problems.
Referring to FIG. 1, a conventional display panel (e.g. LCD panel or PDP) includes a display panel body 1, an inner frame 2 made of synthetic resin in a square shape and coupled to the entire lateral surface of the display panel body 1, and a reinforcement frame 3 having a square overall shape and an L-shaped sectional shape so that it is fastened to the front and lateral surfaces Sf and Ss of the inner frame 2.
Reference numeral H refers to a bolt hole used to couple the reinforcement frame 3 to the inner frame 2.
The reinforcement frame 3 used for the conventional display panel is fabricated by press-working an electric zinc-plated steel plate or a zinc-aluminum-plated steel plate (e.g. galbanum steel plate). However, the fact that the plated steel plate is processed into a square frame by discarding the central portion, which occupies the most area of the plate, to obtain the edge increases the manufacturing cost.
Furthermore, the use of plated steel plates is detrimental to making lighter display panels. If the surface plating is peeled off during transportation or storage, rust may spread on the exposed surface.
It has recently been proposed to separately produce members, which are supposed to constitute respective sides of a square frame, through a press process, for example, arrange the members on a jig so that they overlap each other at a right angle, and subject the overlapping corner portions to spot welding to complete a square frame. However, this type of manufacturing method has a problem in that it is difficult to maintain an appropriate level of bonding strength and that the long welding period increases the manufacturing cost.